Electric arc lamp



June 29, 1937.

s. E. INMAN ET AL 2,085,530

ELECTRIC ARC LAMP Filed June 25, 1932 I F I Z THfRM/ON/CA L L Y ACT/V5 MATfR/AL (20/! TING OF THA-RM/O/V/CALLY ACT/V5 MA TEE/AL INVENTURE GEE/R GE E fzvzmzv EUGENE LEMMER 5 BY fl k/ 27w THEIR. AT TQBNEY Patented June 29, 1937 Lemmers, Cleveland, Ohio, assignors to General Electric Company, a corporation of New York Application June 23, 1932, Serial No. 618,894

11 Claims.

Our invention relates to electric arc lamps of 'he type comprising refractory metal electrodes sealed in a transparent or translucent bulb or other container. One of the objects of our invention is to provide such an arc lamp which will be an efficient source of visible and/or ultraviolet rays and which will operate directly from a line carrying the ordinary commercial voltage without the use of a transformer or other external ballast or equipment.

invention is to provide a combination of elements in the lamp which will increase the ultra-violet efficiency thereof.

According to our invention a lamp comprising an ultra-violet transmitting bulb is filled with a readily ionizable gas such as argon or neon and contains a pair of special electrodes and a resistance heater. Said heater comprises a coil of refractory wire, connected in series with the are 20 ap and encasedin a refractory and insulating tube which extends adjacent to or through a. body of a vaporizable metallic substance, such as mercury or sodium, in said bulb. Said heater is so designed that it will take up the difference 25 in voltage between that on the line and that taken. by the arc itself. This energy is not lost because it greatly increases the efliciency of the are by raising the temperature of the mercury pool to such an extent that the mercury concen- 30 tration in the vicinity of the arc is very high. Said heater is also a source of visible light and infra-red radiation. The electrodes each comprise a surface coated with a thermionically active compound used in combination with a refractory terminal. Said coated surfaces aid in the starting of the arc wherein a glow or diffuse discharge takes place around the electrodes which concentrates, as the temperature and pressure build up, to an are which strikes across the refractory terminals, said terminals being directly in the arc path and closer together than said coated surfaces, The heat from the discharge and the heat radiated from the refractory terminals maintain the coated surfaces in an active 45 condition. Said coated surf-aces therefore serve the double purpose of facilitating starting and aiding in the maintenance of a high pressure are. The refractory terminals serve to collect positive ions and consequently protect the coatings. One of the features of our invention is the disposition of the electrodes longitudinally in the bulb and directlydn the convection stream of vapor arising from the vaporizable metal body, thereby making possible a comparatively long are gap and increasing the ultra-violet'efliciency.

Another object of our Other features and advantages of our invention will appear from the following detailed description of species thereof and from the drawing.

In the drawing Fig. 1 is a perspective view of a lamp comprising our invention; Fig. 2 is a horizontal sectional view of one form of main and auxiliary electrodes; Fig. 3 is a diagrammatic representation of the circuit of the lamp; and Fig.

4 is an enlarged perspective view of a modification of an electrode.

Referring to Fig. 1, the lamp comprises a base in and bulb ll filled with a readily ionizable gas such as argon or neon. A combination electrode comprising a metal member such as a tube 12, preferably of nickel, is mounted on a leading-in Wire l3 which is sealed in a stem tube I4. Instead of the tube l2, a disc or cup may also be used. Said tube l2 has a coating of a thermionically active compound (Fig. 2), preferably an alkaline earth metal compound such as barium oxide on the surface thereof. The tube l2 as shown in the drawing may be closed at the upper end and mounted thereby on the wire I3. Said electrode comprises also a wire I5 extending through said tube I2 and connected thereto at the closed end and carrying a terminal 16 comprising a ball or block of tungsten or other refractory metal which is located just beyond the edge of the tube l2. Said tube l2 may be made of tungsten or Konel metal and in addition to barium oxide the coating thereon may comprise strontium or calcium oxides or combinations thereof.

A second combination electrode comprising a tube l1 and terminal l8, similar to l2|6, is located near the bottom of the bulb ll, both of said electrodes in the form shown being located substantially in the axis of said bulb. Said electrode l'l'--l8 is. mounted on a lead wire l9 which is sealed in the stem tube l4 and is enclosed for nearly its whole length in a quartz tube 20. A 40 third electrode which may be added to facilitate starting comprises a metal body, preferably a tube 2| which also has a coating of a thermionically active compound on the surface thereof. Said tube 2| is mounted very close to tube l2 on a lead wire 22 sealed in the stem tube It. A heater comprising a coil 23 preferably of tungsten or nichrome is mounted on lead wires 24, 25 which are sealed in the stem tube l4. Said heater 23 is encased in a refractory tube 26, preferably of beryllium oxide, which is formed into substantially a U-shape, the legs of the U extending along the gap between the electrodes and the bent to the stem tube H to which they may be sealed,

thereby preventing the formation of an arc at said lead wires 24, 26.. Although beryllium oxide is to be preferred for the tube 26, other refractory substances may be used, such as thoria,

alumina or magnesia. The lower electrode |'|-|6 may support the tube 26 by means of a wire 36 coiled thereabout and sealed in a glass bead 3|. A short wire support 32 is also sealed inthe bear 3| and is mounted on the lead wire I9. Referring to Fig. 3, the preferred circuit through the lamp is from leading-in wire 24 through the heater and ballast resistance 23, lead wire 25, through a relatively high resistance 33 (located in the base l6), lead wire 22, starting electrode 2|, upper electrode |2-|6 and leadingin wire I 3. At the start, a glow discharge takes place between the auxiliary electrode 2| and the tube 2 and a second glow discharge takes place around the lower electrode tube I! which is connected by the lead wire l9 to the wire 26. Said discharges increase in size and strength as the temperature and pressure build up within the lamp until an arc discharge is formed which strikes across terminals l6, l6 since they are closer together than the tubes l2, ll. When the arc has formed, the resistance 33 and electrode 2| are substantially cut out of the circuit, practically all the current going through the arc. It is possible, with the proper combination of purity and composition of gas and proper activity of electrode surfaces, to dispense with the auxiliary electrode 2| and cause an arc to strike directly across the main electrodes.

A modified construction for the electrodes is shown in Fig. 4 and comprises a support wire 34 carrying a ball or block 35, preferably of tungsten, on the end thereof. A coiled wire 36, also preferably of tungsten, is wound around the support wire 34, thus forming a coiled coil, and may be spot welded thereto at each end. To provide more surface we prefer to wind a plurality of layers of coil 36, three being shown in the figure. The coil 36 is then dipped in a solution of a thermionically active compound, such as barium carbonate, and the ball 35 is wiped clean. A length of wire 31 is then wound about the support wire 34 immediately below the coiled coil 36 and the resulting helix is enlarged so as to surround said coiled coil, being spaced therefrom. After the electrode has been mounted in the lamp and during the process of evacuation, said lamp is inserted in an induction coil and the helix 31 becomes intensely heated, thereby driving carbon dioxide out of the barium carbonate with which the coiled coil 36 has been impregnated, leaving a deposit of barium oxide thereon.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An enclosed arc device comprising a bulb,

refractory metal electrodes in said bulb, a coating,

of a thermionically active material on said electrodes, a quantity of. vaporizable metal in said bulb, and a resistance in series with one of said electrodes having a covering of refractory insulating material extending through said vaporizable metal.

2. An enclosed arc device comprising a bulb, refractory metal electrodes in said bulb, a coating of a thermionically active material on said electrodes, a quantity of mercury in said bulb, and a resistance in series with one of said electrodes having a covering of refractory insulating material extending through said mercury.

3. An enclosed arc device comprising a bulb containing an ionizable medium, a pair of main refractory metal electrodes in said bulb each having a coating of a thermionically active material, a resistance in series with one of said main electrodes and an auxiliary electrode mounted adjacent to but spaced from the other of said main electrodes, said auxiliary electrode being connected to the first of said main electrodes and having a resistance in series therewith.

4. An enclosed arc device comprising a bulb containing an ionizable medium, a pair of main refractory metal electrodes in said bulb each having a coating of a thermionically active material,

a resistance in series with one of said main electrodes and an auxiliary electrode mounted adjacent to but spaced from the other of said main electrodes, a coating of a thermionically active material on said auxiliary electrode, said auxiliary electrode being connected to the first of said main electrodes and having a resistance in series therewith.

5. In a device of the class described, an electrode comprising a support wire, a winding of coiled wire about a portion of said support wire adjacent to the end thereof, a thermionically active compound disposed in the turns of said coiled wire, and a tube surrounding said winding of coiled wire, said tube being mounted on said support wire.

6. In a device of the class described, an electrode comprising a support wire, a winding of coiled wire about a portion of said support wire adjacent to the end thereof, a thermionically active alkaline earth metal compound disposed in the turns of said coiled wire, and a helix of wire surrounding said winding of coiled wire, said helix being mounted on said support wire and being spaced from said winding of coiled wire.

7. An electric lamp of the high pressure concentrated arc type comprising a bulb, a quantity of vaporizable metal in said bulb, a pair of spaced refractory metal electrodes in said bulb having associated therewith a thermionically active material for initiating an electric discharge, a substantially U-shaped resistance heater in said bulb having a covering of insulating material thereon, the legs of said U extending along the arc gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending adjacent said vaporizable metal so as to heat the said vaporizable metal and increase the concentration of the vapor thereof in the arc gap during the operation of the lamp, said electrodes being so disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said vaporlzable metal.

v 8. An electric lamp'of the high pressure concentrated arc type comprising a bulb, a quantity of vaporizable metal in said bulb, a pair of spaced refractory .metal electrodes in said bulb having associated therewith a thermionically active material for initiating an electric discharge, a ballast resistance heater in said bulb in series with the arc gap between said electrodes, said heater being substantially U-shaped and having a covering of insulating material thereon, the legs of said U extending along the arc gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending adjacent said vaporizable metal so as to heat the said vaporizable metal and increase the concentration of the vapor thereof in the arc gap during the operation of the lamp, said electrodes being so disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said vaporizable metal.

bulb in series with the arc gap between said elec- 1 trodes, said heater being substantially u-shaped and having a covering of insulating material thereon, the legs of said U extending along the arc gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending adjacent said mercury so as to heat the said mercury and increase the concentration of the vapor thereof in the arc gap during the operation of the lamp, said electrodes being SOi disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said mercury.

10. An electric lamp of the high presure concentrated arc type comprising a bulb, a quantity of vaporizable metal in said bulb, a pair of spaced refractory metal electrodes in said bulb having associated therewith a thermlonically active material for initiating an electric discharge, a substantially U-shaped resistance heater in said bulb having a covering of insulating material thereon, the legs of said U extending along the arc gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending through said vaporizable metal said electrodes being so disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said vaporizable metal.

11. An electric lamp of the high pressure concentrated arc type comprising a bulb, a quantity of vaporizable metal in said bulb, a pair of spaced refractory metal electrodes in said bulb having associated therewith a thermionically active material for initiating an electric discharge, a ballast resistance heater in said bulb in series with the arc gap between said electrodes, said heater being substantially U-shaped and having a covering of insulating material thereon, the legs of said U extending along the are gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending through said vaporizable metal, said electrodes being so disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said vaporizable metal.

GEORGE E. INMAN. EUGENE LEMMERS. 

